A lithographic apparatus is a machine that applies a desired pattern onto a target portion of a substrate. Lithographic apparatus are conventionally used, for example, in the manufacture of integrated circuits (ICs), flat panel displays and other devices involving fine structures.
It is desirable to reduce the size of features in a lithographic pattern because this allows for a greater density of features on a given substrate area. In photolithography, the increased resolution can be achieved by using light of shorter wavelength. However, there are problems associated with such reductions. Current systems are starting to adopt optical sources with wavelengths in the 193 nm regime, but even at this level, diffraction limitations become a barrier. At lower wavelengths, the transparency of materials is very poor. Optical lithography machines capable of enhanced resolutions require complex optics and rare materials and are consequently very expensive.
An alternative for printing sub-120 nm features, known as imprint lithography, comprises transferring a pattern to a substrate by imprinting a pattern into an imprintable medium using a physical mold or template. The imprintable medium can be the substrate or a material coated on to a surface of the substrate. The imprintable medium can be functional or can be used as a “mask” to transfer a pattern to an underlying surface. The imprintable medium can, for example, be provided as a resist deposited on a substrate, such as a semiconductor material, to which the pattern defined by the template is to be transferred. Imprint lithography is thus essentially a molding process on a micrometer or nanometer scale in which the topography of a template defines the patterns created on a substrate. Patterns can be layered as with optical lithography processes so that in principle imprint lithography could be used for such applications as IC manufacture.
The resolution of imprint lithography is limited only by the resolution of the template fabrication process, for example, imprint lithography has been used to produce features in the sub-50 nm range with significantly improved resolution and line edge roughness compared to that achievable with conventional optical lithography processes. In addition, imprint processes do not require expensive optics, advanced illumination sources, or specialized resist materials typically required by optical lithography processes.
Current imprint lithography processes can have a number of drawbacks particularly with regard to achieving overlay accuracy and high throughput. However, significant improvements in resolution and line edge roughness attainable are from imprint lithography.
Imprint lithography is being used to form memory disks or memory platens that adhere to an ever increasing requirement for very dense data bit formation. However, forming denser data bits means each bit must be smaller and closer together. This closeness of the data bits can lead to data bits becoming unstable, either through thermal influences or outside magnetic influences (e.g., through superpara magnetism).
Therefore, what is needed is a system and method that can form dense and relatively small isolated data bits that will remain stable even when influenced by extraneous magnetic and thermal influences, for example through forming them as discrete isolated islands of magnetic material.